Phosphor for thermoluminescent radiation dosimeter

ABSTRACT

A phosphor for a thermoluminescent radiation dosimeter, which is composed primarily of beryllium oxide doped with at least one activator selected from the group consisting of lithium, sodium, potassium, silicon, germanium, tin, zinc, cadmium, aluminum, thallium, cadmium and ytterbium, and which is especially adapted for measuring the dose absorbed by a tissue as its effective atomic number is approximately the same as that of the tissue, and has an excellent sensitivity and retention of radiation energy absorbed.

O United States Patent [1 1 3,6375% Nada et al. 1 Jan. 25, 11972PHOSPHOR FOR {56] References Cited THERMOLUMINESCENT RADIATION UNITEDSTATES PATENTS DOSIMETER 3,463,664 8/1969 Yokota et al, ..252/30l.4 P[72] Inventors: Naohiro Nada, Nishmomlya-shi; Tadaoki Yamashita,Hirakata-shi, both of Japan Primary Examiner Robert Edmonds 73 Assignee:Matsushita Electric Industrial Co., Ltd., Ammewstevensr Dam, & M$herOsaka, Japan [57] ABSTRACT [22] Filed: Mar. 1, 1968 I A phosphor for athermolummescent radiation dos|meter, PP NOJ 709,739 which is composedprimarily of beryllium oxide doped with at least one activator selectedfrom the group consisting of lithium, sodium, potassium, silicon,germanium, tin, zinc, cadmi- [30} Forelgn Application pnomy Data um,aluminum, thallium, cadmium and ytterbium, and which Oct. 12, 1967 Japan..42/6621 1 is especially adapted for measuring the dose absorbed by atis- Oct. 12, i967 Japan ..42/66212 sue as its effective atomic numberis approximately the same Feb. 9, 1968 Japan ..43/8656 as that of thetissue, and has an excellent sensitivity and retention of radiationenergy absorbed. [52] US. Cl. ..252/30l.4 R, 252/301 .4 F, 250/7l.5 5 l1 1m. (:1. ..C09k 1/10 9 Claims, 8 Drawin: Figures [58] Field of Search..250/83 CD, 71.5; 252/3014 PHOSPHOR FOR THERMOLUMINESCENT RADIATIONDOSIMETlElR The present invention relates to a novel phosphor for athermoluminescent radiation dosimeter which is especially adapted foruse in the measuring of the dose absorbed by the tissue and has anexcellent sensitivity and retention of radiation energy absorbed.

in the past, there have been proposed a variety of methods for measuringradiation. A radiation dosimeter primarily resorts to such property of acertain kind of phosphor that absorbs and retains energy commensuratewith a radiation dose. Such a phosphor when heated emits the radiationenergy absorbed thereby in the form of light, so that by measuring theamount of the light by a suitable instrument, it is possible to obtainthe radiation dose.

The relationship between the light emitted by a thermoluminescentphosphor and the temperature of said thermoluminescent phosphor whensaid thermoluminescent phosphor is heated at a constant rate isrepresented by the so-called glow curve. The size of the glow curve isrelated with the sensitivity of the phosphor, while the temperaturecorresponding to the glow peak is closely related with the absorbedradiation energy retention of the pertinent phosphor. Namely, thegreater the glow curve, the better the sensitivity to radiation of aphosphor and the higher the temperature for the glow peak, the betterthe radiation energy retention of the phosphor is, although thetemperature for the glow peak is somewhat variable depending upon therate at which the phosphor is heated.

The phosphor used in conventional thermoluminescent radiation dosimetersinclude lithium fluoride (LiF), calcium fluoride doped with manganese(CaF :Mn) and calcium sulfate doped with manganese (CaSOpMn). Of thesephosphors, lithium fluoride is most suitably used for quantitativelymeasuring the radiation dose absorbed by a tissue. This is becauselithium fluoride has a radiation-absorbing property similar to that ofthe tissue by virtue of the fact that the atomic numbers of theconstituent elements are low and close to the effective atomic number ofthe tissue, and therefore exhibits substantially the same sensitivityfor X-rays or y-rays of various wavelengths. However, lithium fluoridehas disadvantages in respect of its sensitivity and stability inrepetitive measurement. On the other hand, CaF zMn and CaSO :Mn have thedrawback that they are not adapted for use in measuring X- rays of anenergy smaller than 200 KeV because, since the atomic numbers of theconstituent elements thereof are considerably larger than the effectiveatomic number of the tissue, the measurement error is extremely great,though they do not have the problem of deterioration.

The object of the present invention is to provide a phosphor for athermoluminescent radiation dosimeter, which has an excellentsensitivity and radiation energy retention, and which is composedprimarily of beryllium oxide (BeO) the effective atomic number of whichis very close to that of the tissue.

FIGS. 1 to 5 inclusive are charts showing the thermoluminescent glowcurves of the thermoluminescent phosphors according to the presentinvention.

FIG. 6 is a set of views showing thermoluminescent elements produced bythe use of the inventive phosphors.

The effective atomic number of beryllium oxide is 7.2 which is close tothat of the tissue which is 7.4. Obviously therefore, beryllium oxide iscapable of measuring a radiation absorbed by the tissue more efficientlythan lithium fluoride whose effective atomic number is 8.1. Now, theprocess for the production of the inventive phosphor, the properties ofthe phosphor produced and the method of molding the inventive phosphor,will be described in detail hereinafter. The phosphor according to thepresent invention consists primarily of beryllium oxide which is dopedas an activator with at least one element selected from the groupconsisting of lithium (Li), sodium (Na), potassium (K), silicon (Si), grmanium (Ge), tin (Sn), zinc (Zn), cadmium (Cd), aluminum (Al), thallium(Tl), vanadium (V) and ytterbium (Yb).

These impurities to be used as an activator may be added to the matrixconsisting of beryllium oxide by mixing a fine powder of beryllium oxidewith a fine powder of the activator homogeneously with stirring andsintering the resultant mixture at elevated temperature. Instead ofusing beryllium oxide, a salt such as a sulfate of beryllium(BeSO,-4l-l,0) may be used as a starting material. The salt may befinally converted into beryllium oxide when subjected to a heattreatment, since it is decomposedinto an oxide of beryllium at elevatedtemperature. Of the impurities, Li and Na may be used in the form ofmetal or in the form of hydroxide or in the form of such a salt asnitrate, sulfate, carbonate or chloride, instead of oxide thereof. Thesintering is necessarily carried out in the temperature range from l,500to 2,100" 0, because a phosphor having a sufficiently high intensity ofthermoluminescence cannot be obtained at a temperature outside the rangespecified. In order to obtain a satisfactory sintering result andtherefore a satisfactory intensity of thermoluminescence, the materialmixture is first subjected to a heat treatment at a temperature of l,500C. or higher for several hours, removing the resultant agglomerate fromthe furnace upon cooling, mixing the constituent materials again afterpulverizing said agglomerate and sintering the mixture once again at atemperature of 1,500 C. or higher.

The intensity of thermoluminescence of the product phosphor is alsoinfluenced by the heating atmosphere used. In general, a slightlyoxidizing atmosphere is preferable for obtaining a satisfactorythermoluminescence intensity. The use of a reducing atmosphere will onlyresult in a weak thermoluminescence intensity of the product phosphor.By changing the elements to be added as impurities, phosphors ofvariable properties can be obtained. A phosphor which is produced bysubjecting BeO alone is of course very low in termoluminescenceintensity. In practice, a phosphor consisting solely of BeO has athermoluminescence intensity which is as low as about one hundredth ofthat of a phosphor which is produced under optimum conditions as will beset forth later. The highest thermoluminescence intensity of phosphorcan be obtained when Li, Na or K is used as an additive.

in using Na, the thermoluminescence intensity of a product phosphor ismainly varied depending upon the amount in which it is added and theheat treatment conditions. Besides these factors, the form in which Nais added also has some bearing on the thermoluminescence intensity ofthe product phosphor. Heat treatment is preferably conducted at a highertemperature and must be within the temperature range from 1,500 to 2,100C. Use of a temperature lower than that specified will not yield aphosphor having a sufficiently high intensity of thermoluminescence. Itis also to be noted that a higher thermoluminescence intensity can beobtained by carrying out the heat treatment in an oxidizing atmosphere,e.g., in the air or in oxygen atmosphere, than in other atmospheres.Heat treatment in a reducing atmosphere, such as argon admixed with 5percent of hydrogen, will only result in a weak thermoluminescenceintensity of the product phosphor. Further, a better result can beobtained by carrying out the sintering for a longer period and thesintering must be effected for at least 1 hour. In practice, however, aperiod of about 3 hours is sufficient for the sintering. Consequently,the heat treatment is preferably carried out at a temperature of l,700C. for 3 hours in the atmosphere. The thermoluminescence intensity ofthe product phosphor is also altered slightly by the form of Na compoundused as an additive, even though the heat treatment is conducted underthe same conditions. The highest intensity of thermoluminescence ofphosphor can be obtained when Na is used in the form of Na SO Use of Nain the form of NaOH or Na CO will only yield a phosphor whosethermoluminescence intensity is lower than that produced using Na in theform of Na,so,. Since these sodium salt evaporate when heated to a hightemperature, beryllium oxide resulting from sintering at elevatedtemperature contains only a part of the amount in which Na was initiallyadded. From only the relation between the form of a compound in which Nais added and the thermoluminescence intensity of the product phosphor,it appears that a phosphor of higher thermoluminescence intensity may beobtained by adding Na in the form of a compound which will evaporate inlesser amount at elevated temperature than others.

Now, even when Na is added in the form of Na,SO,, the resultantthermoluminescence intensity of the product phosphor is variabledepending upon the amount of Na,SO added and the thermoluminescenceintensity obtained is illustrated in the chart of FIG. 1. In this chart,the curves show the thermoluminescence intensities of the phosphorswhich were produced by the use of Na SO, in amounts of mol percent, 5mol percent, 1.5 mol percent and 0.5 mol percent individually andcarrying out the sintering at 1,700 C. for 3 hours in the atmosphere.The flame analysis of the beryllium oxides obtained after sintering withNa SO added in the amounts depicted above, indicated that they containedNa in amounts of 0.07 mol percent, 0.07 mol percent, 0.02 mol percentand 0.008 mol percent respectively. Such an amount of Na which isdetermined by analysis will hereinafter be referred to as Na content.The best Na content in beryllium oxide after sintering is 0.07 molpercent in concentration, although a slight deviation from saidconcentration of Na will not give much detrimental affect on thethermoluminescence intensity of the product phosphor. As may beunderstood from the chart, the thermoluminescence intensity of aphosphor the Na content of which is 0.008 mol percent or 0.5 molpercent, is about one-fifth of that of a phosphor containing 0.07 molpercent of Na, and the thermoluminescence intensities of phosphorshaving an Na content within the range from 0.005 to 0.5 mol percent aresufficiently high. It will also be seen from the chart of FIG. I thatthe glow curve forms a peak at a temperature of 182 C. indicating thatthe phosphors are also relatively satisfactory in respect of radiationenergy retention. The glow curves shown are drawn based upon the resultsobtained on heating the phosphors at the rate of 30 C. per minute. Theshapes of the glow curves will vary slightly as the heating rate varies.The other glow curves which will be illustrated hereinafter are alsodrawn based on the measurements taken when the pertinent phosphors wereheated at the rate of 30 C. per minute.

In the case of K, the peak of the glow curve is located at a temperaturein the vicinity of about 182 C. and the best content of K is very closeto that in the case of Na. In the case of Li, the best content thereofis about the same as that for Na but, unlike the cases of Na and K, theglow curve of a phosphor containing Li forms a peak at a temperature aslow as about 162 C. as shown in FIG. 2.

The main glow curves of phosphors produced with the addition of otherimpurities, i.e., Si, Ge, Sn, Zn, Cd, TI and V, individually, form apeak mostly at a temperature of 182 C. The thermoluminescenceintensities of these phosphors are variable depending upon the impurityelement used. When the impurity content is within the range from 0.01 to3 mol percent, the thermoluminescence intensities of these phosphors arefrom one-fifth to one-tenth of that of a phosphor containing Na. Some ofthese phosphors, though inferior to a Na-containing phosphor in respectof thermoluminescence intensity, have a glow peak at a temperaturehigher than that of Na-containing phosphor and accordingly are superiorto the latter in respect of retention of the radiation energy absorbedthereby. The elements which enable a high-glow peak temperature to beobtained are Si and Ge which are elements in Nb Group of the PeriodicTable. The phosphors containing Si and Ge have a glow peak at atemperature of about 195 C. As shown in FIG. 3, the thennoluminescenceintensity of Si-containing phosphor is satisfactorily high when the Sicontent is within the range from 0.01 to 5 mol percent and highest whenthe Si content is about 0.3 mol percent. Si is added in the form of SiO,which will not substantially evaporate during sintering at elevatedtemperature. Therefore, Si is contained in the beryllium oxide aftersintering in the same amount as was originally added. When Al or Yb isadded, the glow curve of the product phosphor forms a subglow peak, inaddition to the main glow peak at a temperature of 190 C., at about 310C. as indicated by a curve (0) in the chart of FIG. 4.

Although the foregoing description has been made with particularreference to those phosphors which are produced with the addition ofsingle impurity element, phosphors produced with the addition of two ormore elements at the same time exhibit a property which is a combinationof the individual phosphors produced with the addition of each of saidelements. Therefore, by selecting the elements to be used simultaneouslyfrom the group of elements mentioned previously, the property of theproduct phosphor will not extremely be deteriorated by the addition ofan additional element. In some cases, the property of the productphosphor may rather be improved by the use of elements in combination.For instance, by the use of Li in combination with a suitable amountofSi, it is possible to raise the glow peak position to a highertemperature side with no substantial adverse affect on the sensitivity.The same effect can be obtained when at least one element selected fromthe group consisting of Li, K and Na is used in combination with a smallamount of at least one element selected from the group consisting of Siand Ge. However, inclusion of elements other than those depictedpreviously, e.g., iron (Fe), cobalt (Co) or nickel (Ni), even in a smallamount, will result in sharp lowering of the thermoluminescenceintensity.

In the foregoing description, use is made of an oxidizing atmosphere forsintering. Use of reducing atmosphere for the sintering, e.g., sinteringin argon gas containing 5 percent of hydrogen, will only result in aphosphor having a low thermoluminescence. In this case, however, thethermoluminescence at 200 C. or higher reduces drastically and aphosphor with which a dose can be measured with a small error can beobtained. The glow peak temperature also is also varied somewhat by thetype of atmosphere used.

In order that the present invention may be more clearly understood, thepresent invention will be further illustrated by way of examples thereofbut it is to be understood that the present invention is not restrictedonly thereto.

EXAMPLE I A mixture of 0.1 mol of beryllium oxide (BeO) and 0.005 mol ofsodium sulfate (Na SO was sintered at 1,700 C. for 3 hours in theatmosphere and a thermoluminescent phosphor of a thermoluminescent glowcurve as indicated by (a) in the chart of FIG. 4 was obtained. Thematerial beryllium used was a product of Nippon Gaishi Kaisha, Ltd.having a superhigh purity. The beryllium oxide contained Si, Ca and Naas major impurities, the amounts of which are as small as less thanp.p.m. respectively. The sodium sulfate used was one which is being soldon the market as a reagent and the purity of this degree is sufficientfor use. Describing the process more practically, 0.1 mol of berylliumoxide and 0.005 mol of sodium sulfate, after weighing individually, weremixed and stirred in a commercial mixer to produce a homogeneousmixture. The mixture was placed in a beryllia crucible and sintered in ahigh frequency furnace at l,700 C. for 3 hours in the atmosphere. Inthis case, if the temperature is low, substantially no reaction takesplace between beryllium oxide and sodium sulfate, so that sodium willnot be diffused into the beryllium oxide. In order to obtain asufficient diffusion, the sintering should be effected at l,500 C. orhigher and further the reactants should be reduced in particle size tothe possible extent beforehand. On the contrary, if the sinteringtemperature is too high, the sodium sulfate added will evaporate, withthe result that only a very small amount of sodium sulfate is present inthe beryllium oxide after sintering. The result of the quantitativeanalysis has revealed that when the sintering is effected at l,700 C.,the amount of sodium contained in the sintered beryllium oxide is onlyabout one-hundredth of that originally added. The sintering can besufficiently accomplished in a period of about 3 hours. Further, thesintering is preferably carried out in an oxidizing atmosphere such asair or oxygen, and sintering in a reducing atmosphere, such as argoncontaining 5 percent of hydrogen will only result in an insufficientthermoluminescence intensity of the product phosphor. Use of NaOH or NaCQ, in place of Na SO is not advantageous because these compoundsevaporate more intensely than Na,SO during the sintering operation atelevated temperature, enabling only a phosphor of low-thermoluminescenceintensity to be obtained.

EXAMPLE 2 A mixture of 0.1 mol of beryllium oxide (BeO) and 0.01 mol ofpotassium hydroxide was sintered in air at 1,500 C. for 3 hours and athermoluminescent phosphor was obtained which had a thermoluminescentglow curve essentially similar to the glow curve (a) in FIG. 4. Thethermoluminescence intensity of the product phosphor becomes lower asthe sintering temperature lowers. For instance, the thermoluminescenceintensity of the phosphor obtained by sintering at 600 C. is about oneone-hundredth of that of the phosphor obtained by sintering at 1,500 C.,and that of the phosphor obtained by sintering at 900 C. is aboutone-tenth of the latter. The use of a lower temperature for sinteringalso renders the glow curve of the product phosphor complicated. Namely,the glow curve will form a peak at a temperature of 310 C., in additionto the peak at a temperature of 182 C. In order to obtain a sufficientlyhigh-thermoluminescence intensity, the sintering must be effected at atemperature at least not lower than 1,500 C. The rate of heating orcooling during the heat treatment has substantially no bearing on thethermoluminescence intensity of the product phosphor. However, it shouldbe noted that sintering in a reducing atmosphere of argon gas,containing 5 percent of hydrogen, at 1,500 C. will only result in aphosphor the thermoluminescence intensity of which is about one-half ofthat of the phosphor obtained by sintering in air.

EXAMPLE 3 A mixture of 0.1 mol of beryllium oxide (BeO) and 0.0001 molof zinc oxide (ZnO) was processed in the same manner as in example 1 anda thermoluminescent phosphor was obtained whose thermoluminescent glowcurve was as indicated by (b) in the chart of FIG. 4.

EXAMPLE4 A mixture of 0.1 mol of beryllium oxide (BeO) and 0.00005 molof aluminum oxide (A1 was processed in the same manner as in example 1and a thermoluminescent phosphor was obtained whose thermoluminescentglow curve was as indicated by (c) in the chart of FIG. 4.

EXAMPLE A mixture of 0.1 of beryllium oxide, 0.0002 mol of lithiumcarbonate (Li CO and 0.001 mol of silicon oxide (SiO was sintered at1,500 C. for 3 hours in air and a thermoluminescent phosphor wasobtained whose thermoluminescent glow curve was as indicated by (a) inthe chart of FIG. 5.

EXAMPLE 6 A mixture of 0.1 mol of beryllium oxide (BeO), 0.005 mol ofsodium sulfate (Na SO 0.001 mol of lithium carbonate (Li CO and 0.0001mol of aluminum oxide (A1 0 was processed in the same manner as inexample 5 and a thermoluminescent phosphor was obtained whosethermoluminescent glow curve was as indicated by (b) in the chart ofFIG. 5.

To this point, a description has been given as to the method of and theconditions for activating thermoluminescent phosphors. Now, a method ofshaping the thermoluminescent phosphors will be described hereinafter.The shaping is necessary to facilitate the handling of thermoluminescentphosphors which in a powdery state are obviously inconvenient inhandling.

A first method of producing a shaped thermoluminescent phosphor is tosinter a material mixture after shaping it by cold pressing. In thiscase, the heat treatment required for the activation of the phosphor andthe heat treatment required for the shaping may be accomplishedsimultaneously and the working efiiciency can be improved in this way.In practice, a material mixture consisting of beryllium oxide and animpurity or impurities is homogeneously mixed with stirring and, aftershaping by a cold press, the shaped mixture is sintered at a temperaturenot lower than 1,500 C. to solidify the same. The shaping temperature isvariable depending upon the type and amount of the impurity added. Forinstance, beryllium oxide doped with 10 mol percent of NaOH may besufficiently shaped at a temperature of l,600 C. A higher temperature isrequired for the shaping of beryllium oxide doped with 0.01 mol percentof A1 0 i.e., the shaping in this case can be accomplished at atemperature of l,800 C. or higher. It is to be noted, however, that theshaping can be accomplished at a lower temperature if the berylliumoxide is doped with a small amount of a flux, such as NaOI-I, inaddition to A1 0 The shaping temperature may be lowered somewhat byemploying a hot press.

A second method of producing a shaped thermoluminescent phosphor is toshroud the surface of a shaped phosphor obtained by cold pressing athermoluminescent powder or coating the surface of a shapedthermoluminescent phosphor obtained by the first method described above,with glass. This method is particularly advantageously used forproducing a shaped thermoluminescent phosphor which is susceptible todeterioration when left to stand in the atmosphere for a prolongedperiod. In this case, use of a glass having a low melting point isadvantageous in working. Further, it is important to use a glasscomposed of lighter elements. A glass to be used should be composed atleast of such elements whose atomic numbers are smaller than that ofzinc. Use of a lead-type glass is not satisfactory in respect ofradiation absorption because of the large atomic number, although it islow in melting point and easy to work. In practice, silicateorborate-type glasses are preferably used. Described above are almost allrestrictions which are imposed on the composition of the glass used.These glasses or glazes are applied on the surfaces of a BeO sheetmaterial in the form of a dispersion in water and thereafter the glassorglaze-coated BeO sheet is sintered at a temperature of about l,000 C.The glazing treatment commonly practiced in the ceramic industry can beapplied as such to the coating operation.

A third method of producing a shaped thermoluminescent phosphor is tomix a powdery thermoluminescent phosphor material with a glass powderand then the resultant mixture is heated, whereby the thermoluminescentphosphor material is solidified with the molten glass. Thethermoluminescent phosphor obtained by this method is somewhat defectivein respect of transparency. Namely, since BeO is dispersed in the glass,the product thermoluminescent phosphor element presents a frostedappearance compared with those produced by the first and second methodsdescribed above, and accordingly the thermoluminescent intensity of thephosphor element is reduced to some extent. However, this method is veryconveniently used in producing thermoluminescent phosphor elements ofvarious shapes quickly. The methods of producing shapedthermoluminescent phosphor elements described hereinabove will befurther illustrated with reference to examples thereof.

EXAMPLE 1 A mixture of 0.01 mol of beryllium oxide (BeO) and 0.0005 molof sodium sulfate (Na SO was shaped by cold pressing under a pressure of1,000 kilograms per square centimeter and the resultant shaped mixturewas sintered at l,700 C. for 3 hours in air. A shaped thermoluminescentphosphor element was obtained as indicated by numeral 1 in FIG. 6a. Bythis method, a thermoluminescent phosphor of any desired shape can beobtained which is convenient in handling as a dosimeter.

1 EXAMPLE 2 A mixture of0.0l mol of beryllium oxide (BeO) and 0.0005 molof lithium carbonate Li,co,) was sintered at 1,700 C. for 3 hours in airand the thermoluminescent phosphor thus obtained was shaped by coldpressing. After coating the surfaces of the shaped phosphor with a glass(a borosilicate glass), a shaped phosphor element was obtained as shownin FIG. 6b wherein numeral 1' designates the shaped phosphor and 2designates the glass coating. The shaped phosphor element with a glasscoating thereon is not toxic to the user, though BeO is slightly toxicper se.

EXAMPLE 3 A mixture of 0.01 mol of beryllium oxide (BeO) and 0.00003 molof silicon oxide (SiO was sintered at 1,700 C. for 3 hours in air andthe sintered mixture was mixed with a glass powder composed of 72percent by weight of SiO,, l percent by weight of Na O, 9 percent byweight of CaO, 3 percent by weight of MgO and 1 percent by weight ofAi,o,. The resultant mixture was heated at l,000 C. for 1 hour in airand a shaped phosphor element as shown in FIG. 6c was obtained. In theFigure, numeral 1' designates the thermoluminescent phosphor and 2'designates the glass. The shaped phosphor element of this type is alsoadvantageous in that it is not toxic to the user as in the precedingexample.

What is claimed is:

l. A phosphor for a thermoluminescent radiation dosimeter, consistingprimarily of beryllium oxide doped with 0.005 to 0.5 mol percent of atleast one activator selected from the group consisting of lithium,sodium and potassium and 0.01 to 5 mol percent of at least one activatorselected from the group consisting of silicon and germanium.

2. A phosphor for a thermoluminescent radiation dosimeter, consistingprimarily of beryllium oxide doped with 0.005 to 0.5 mol percent of atleast one activator selected from the group consisting of lithium,sodium and potassium.

3. A process for the production of the phosphor for a thermoluminescentradiation dosimeter claimed in claim 1, comprising mixing at least onematerial selected from the group consisting of beryllium oxide andberyllium sulfate with at least one activator selected from the groupconsisting of lithium, sodium and potassium and the oxides, hydroxides,nitrates, sulfates, carbonates and chlorides thereof and at least oneactivator selected from the group consisting of silicon oxide andgermanium oxide, shaping said mixture by press molding, sintering themixture at a temperature of l,500 to 2,l00 C. in an oxidizingatmosphere.

4. A process for the production of the phosphor for a thermoluminescentradiation dosimeter claimed in claim 2, comprising mixing at least onemember selected from the group consisting of beryllium oxide andberyllium sulfate with at least one activator selected from the groupconsisting of lithium, sodium, potassium, and the oxides, hydroxides,nitrates, sulfates, carbonates and chlorides thereof, shaping saidmixture by press molding, sintering the mixture at a temperature ofl,500 to 2,100 C. in an oxidizing atmosphere.

5. A process for the production of a phosphor for a thermoluminescentradiation dosimeter, which comprises mixing a material beryllium oxidewith at least one activator selected from the group consisting oflithium, sodium, potassium, and the oxides, hydroxides, nitrates,sulfates, carbonates and chlorides thereof, shaping said mixture bypress molding, sintering the mixture at a temperature of l,500 to 2,100"C. in an oxidizing atmosphere and coating the surfaces of the resultantshaped phosphor with a glass.

6. A process for the production of a phosphor for a thermoluminescentradiation dosimeter, which comprises mixing a material beryllium oxidewith at least one activator selected from the group consisting ofsilicon oxide and germanium oxide, shaping said mixture by pressmolding, sintering the mixture at a temperature of l,500 to 2,l00 C. inan oxidizing atmosphere and coating the surfaces of the resultant shapedphosphor with a lass.

7. A method or producing a thermoluminescent radiation dosimeterphosphor comprising:

mixing at least one material selected from the group consisting ofberyllium oxide and beryllium sulfate with at least one member selectedfrom the group consisting of materials which provide either lithium,sodium, potassium, silicon, germanium, tin, zinc, cadmium, aluminum,thallium, vanadium or ytterbium as activator, shaping said mixture bypress molding, and thereafter sintering the mixture at a temperature ofl,500

to 2,l00C. 8. A process for producing a thermoluminescent radiationdosimeter phosphor comprising:

mixing at least one material selected from the group consisting ofberyllium oxide and beryllium sulfate with at least one activatingmaterial selected from those which provides either lithium, sodium,potassium, silicon, germanium, tin, zinc, cadmium, aluminum, thallium,vanadium or ytterbium, sintering the mixture at a temperature ofl,500-2,100 C.

in an oxidizing atmosphere, shaping thus sintered product by pressmolding and coating the molded product with glass. 9. A process forproducing a thermoluminescent radiation dosimeter phosphor comprising:

mixing at least one material selected from the group consisting ofberyllium oxide and beryllium sulfate with at least one activatingmaterial selected from those which provides either lithium, sodium,potassium, silicon, germanium, tin, zinc, cadmium, aluminum, thallium,vanadium or ytterbium, sintering the mixture at a temperature ofl,5002,l00 C.

in an oxidizing atmosphere and shaping and solidifying thus sinteredproduct with a binder of glass.

2. A phosphor for a thermoluminescent radiation dosimeter, consistingprimarily of beryllium oxide doped with 0.005 to 0.5 mol percent of atleast one activator selected from the group consisting of lithium,sodium and potassium.
 3. A process for the production of the phosphorfor a thermoluminescent radiation dosimeter claimed in claim 1,comprising mixing at least one material selected from the groupconsisting of beryllium oxide and beryllium sulfate with at least oneactivator selected from the group consisting of lithium, sodium andpotassium and the oxides, hydroxides, nitrates, sulfates, carbonates andchlorides thereof and at least one activator selected from the groupconsisting of silicon oxide and germanium oxide, shaping said mixture bypress molding, sintering the mixture at a temperature of 1,500* to2,100* C. in an oxidizing atmosphere.
 4. A process for the production ofthe phosphor for a thermoluminescent radiation dosimeter claimed inclaim 2, comprising mixing at least one member selected from the groupconsisting of beryllium oxide and beryllium sulfate with at least oneactivator selected from the group consisting of lithium, sodium,potassium, and the oxides, hydroxides, nitrates, sulfates, carbonatesand chlorides thereof, shaping said mixture by press molding, sinteringthe mixture at a temperature of 1, 500* to 2,100* C. in an oxidizingatmosphere.
 5. A process for the production of a phosphor for athermoluminescent radiation dosimeter, which comprises mixing a materialberyllium oxide with at least one activator selected from the groupconsisting of lithium, sodium, potassium, and the oxides, hydroxides,nitrates, sulfates, carbonates and chlorides thereof, shaping saidmixture by press molding, sintering the mixture at a temperature of1,500* to 2,100* C. in an oxidizing atmosphere and coating the surfacesof the resultant shaped phosphor with a glass.
 6. A process for theproduction of a phosphor for a thermoluminescent radiation dosimeter,which comprises mixing a material beryllium oxide with at least oneactivator selected from the group consisting of silicon oxide andgermanium oxide, shaping said mixture by press molding, sintering themixture at a temperature of 1,500* to 2,100* C. in an oxidizingatmosphere and coating the surfaces of the resultant shaped phosphorwith a glass.
 7. A method for producing a thermoluminescent radiationdosimeter phosphor comprising: mixing at least one material selectedfrom the group consisting of beryllium oxide and beryllium sulfate withat least one member selected from the group consisting of materialswhich provide either lithium, sodium, potassium, silicon, germanium,tin, zinc, cadmium, aluminum, thallium, vaNadium or ytterbium asactivator, shaping said mixture by press molding, and thereaftersintering the mixture at a temperature of 1,500* to 2,100*C.
 8. Aprocess for producing a thermoluminescent radiation dosimeter phosphorcomprising: mixing at least one material selected from the groupconsisting of beryllium oxide and beryllium sulfate with at least oneactivating material selected from those which provides either lithium,sodium, potassium, silicon, germanium, tin, zinc, cadmium, aluminum,thallium, vanadium or ytterbium, sintering the mixture at a temperatureof 1,500*-2,100* C. in an oxidizing atmosphere, shaping thus sinteredproduct by press molding and coating the molded product with glass.
 9. Aprocess for producing a thermoluminescent radiation dosimeter phosphorcomprising: mixing at least one material selected from the groupconsisting of beryllium oxide and beryllium sulfate with at least oneactivating material selected from those which provides either lithium,sodium, potassium, silicon, germanium, tin, zinc, cadmium, aluminum,thallium, vanadium or ytterbium, sintering the mixture at a temperatureof 1,500*-2,100* C. in an oxidizing atmosphere and shaping andsolidifying thus sintered product with a binder of glass.